Styrene-based polymers produced by radical polymerization and so forth have atactic configuration and are widely used in home electrical appliances, office appliances, home tools, wrapping containers, furniture, synthetic paper, and other industrial materials by molding using techniques such as injection molding, extrusion molding, blow molding, vacuum molding and casting molding.
The styrene-base polymers having atactic configulation, however, have the disadvantages of being poor in mechanical strength, heat resistance and chemical resistance, because the styrene-based polymers do not undergo crystallization.
The present inventors' group have succeeded in producing styrene-based polymers of high syndiotacticity and developed compositions containing these high syndiotacticity styrene-based polymers (see U.S. Pat. No. 4,680,353 and Japanese Patent Application Laid-Open Nos. 104818/1987, 257948/1987 and 257950/1987). These syndiotactic styrene-based polymers or their compositions are excellent in mechanical strength, heat resistance, solvent resistance, electrical characteristics and so forth as compared with atactic styrene-based polymers or their compositions. In molding the syndiotactic styrene-based polymers or their compositions, however, a high molding temperature is needed to crystallize the syndiotactic styrene-based polymers. Moreover, the syndiotactic styrene-based polymers have a low crystallization rate at low temperatures and thus suffer from the disadvantages that the molding cycle is long and flash is readily formed, even if the molding is in a mold maintained at a high temperature.